1. Field of the Invention
The present invention relates to an image processing apparatus, an image forming apparatus, and an image processing method.
2. Description of the Related Art
Generally, in line ink jet recording apparatuses in which a plurality of head units is coupled to record image as much as an amount corresponding to the width of a sheet of paper by only an instance of scanning, or in serial ink jet recording apparatuses that form an image in the one-pass printing mode in which a head records image as much as an amount corresponding to the width of the head by only an instance of scanning, a variation in ejection characteristics of the heads sometimes causes degradation such as unevenness of an image.
Thus, Japanese Patent Application Laid-open No. 2005-219508 discloses a printer allowing an overlap in the main scanning line. However, when the amount of the overlap is very small, it is impossible to completely suppress appearing of the variation in characteristics. Meanwhile, when the amount of the overlap is large, the use efficiency of the head drops and the printing speed is lowered.
For such a reason, Japanese Patent Application Laid-open No. 2004-326613 discloses an image processing method of reducing the banding by changing the driving waveform of the head. In addition, Japanese Patent Application Laid-open No. 2003-189103 discloses an image forming apparatus in which an image of which density uniformity is corrected is produced by superimposing a signal for correcting the in-plane density unevenness on a halftone image.
However, when the printer disclosed in Japanese Patent Application Laid-open No. 2005-219508 is used to resolve the variation in characteristics of the heads, various driving waveforms are necessary. In addition, since the size or the shape of ink drops may vary inside a head, it is difficult to prepare all the driving waveforms in advance.
In addition, the gradation value changes when the image processing method disclosed in Japanese Patent Application Laid-open No. 2004-326613 is used so as to resolve the variation in characteristics of the heads. The change of the gradation value results in a change of a pattern of dot arrangement. Therefore, appears the discontinuity in pattern rather than the discontinuity in a color.
In addition, in order to solve the above-described problems, the present invention may be implemented as an image forming apparatus including the above-described image processing apparatus or an image processing method used in the above-described image processing apparatus.